1. Field of the Invention
The present invention relates to an electrodeless lighting system, and particularly, to an electrodeless lighting system provided with a resonator configured to minimize leakage of microwaves and improve luminous efficiency.
2. Description of the Background Art
In general, an electrodeless lighting system is an apparatus emitting visible light or ultraviolet light from an electrodeless plasma bulb upon applying microwave energy to the bulb. The electrodeless lighting system has a long life span and good lighting effect compared with an incandescent lamp or a fluorescent lamp which is generally used.
FIG. 1 is a longitudinal sectional view showing one example of a conventional electrodeless lighting system.
As shown, the conventional electrodeless lighting system using microwave energy includes: a case 1 forming a certain internal space; a microwave generator 2 mounted in the case 1, for generating microwave energy; a high voltage generator 3 for raising a common AC power to a high voltage and supplying the high voltage to the microwave generator 2; a waveguide 4 for guiding microwave energy generated at the microwave generator 2; a resonator 6 installed at an exit portion 4a of the waveguide 4 to communicate with the waveguide 4; and a bulb 5 positioned in the resonator 6 and emitting light as a filling material becomes a plasma by microwave energy transferred through the waveguide 4.
In addition, a reflecting mirror 7 for concentratively reflecting light generated at the bulb 5 to the front is provided in front of the case 1, a surrounding area of the resonator 6.
A dielectric mirror 8 is installed in the exist portion 4a of the waveguide 4, wherein the dielectric mirror 8 passes microwave energy transferred through the waveguide 4 and reflecting light emitted from the bulb 5 to the front. A hole 8a is formed at a central portion of the dielectric mirror 8 in order that a shaft portion 9 of the bulb 5 penetrates therethrough.
Meanwhile, a cooling fan 10 for cooling the microwave generator 2 and the high voltage generator 3 is provided at the rear of the case 1. And, in the drawing, non-explained reference number 11 indicates a fan motor, and 12 is a bulb motor for rotating the bulb 5.
As for the resonator 6 of the conventional electrodeless lighting system, a perforation ratio per unit area is adjusted to be sufficient to emit light from the bulb to the outside of the resonator.
Also, the size of each perforation constituting a mesh over the entire resonator 6 is determined on the basis of whether a perforation ratio required for light emission is achieved and whether microwave energy is not allowed to leak out of the resonator, simultaneously. As the perforation size of the resonator 6 is bigger, the performance of emitting light is better, but the performance of preventing the microwave energy leakage is worse. On the contrary, as the perforation size of the resonator 6 is smaller, the performance of emitting light is worse, but the performance of preventing the microwave energy leakage is better.
Thus, the conventional resonator 6 has a mesh structure formed of the same sized perforations over its entire area.
The conventional electrodeless lighting system having such a structure is operated as follows.
When a driving signal is inputted to the high voltage generator 3, the high voltage generator 3 raises AC power and supplies the raised high voltage to the microwave generator 2. The microwave generator 2 oscillates by a high voltage to thereby generate microwave energy having a very high frequency. The microwave energy generated in such a manner is guided through the waveguide 4 and is emitted into the resonator 6. The microwave energy emitted in the resonator 6 resonates in the resonator and also is strongly applied to a portion where the bulb 5 of the resonator 5 is positioned. At this time, by electrically discharging a material within the bulb 5, light having its own spectrum is generated. The light is reflected to the front by the reflecting mirror 7 and the dielectric mirror 8, thereby lighting a space.
However, because the conventional electrodeless lighting system is formed in a mesh structure having perforations of uniform sizes in order to achieve an optimum perforation ratio for an entire area of the resonator, when microwave energy is strongly applied around the bulb positioned in the resonator, the amount of microwave energy leaked to the outside of the resonator around the bulb is undesirably higher than that of other portions of the resonator.
Therefore, the amount of the microwave energy applied to the bulb is decreased, thereby degrading luminous efficiency of the bulb.